Embodiments of the invention relate generally to electroerosion machines and, more particularly, to a tube-shaped electrode for electroerosion machines.
Electroerosion machining is a machining method that is generally used for machining hard metals or those that would be impossible to machine with other techniques such as using lathes, drills, or the like. Electroerosion machining can thus be used in trepanning or drilling operations in extremely hard steels and other hard, electrically conductive metals such as titanium, hastelloy, kovar, inconel, carbide, or the like. Certain electroerosion machining techniques utilize electrical discharge and spark eroding to provide a rough machining method that aggressively removes material (e.g., at a rate 10× that of standard electrical discharge machining) by a series of rapidly recurring electric arcing discharges between an electrode (the cutting tool) and the workpiece, in the presence of an energetic electric field. The electroerosion cutting tool is guided along the desired path very dose to the work but it does not touch the piece. Consecutive sparks produce a series of micro-craters on the workpiece and remove material along the cutting path by melting and vaporization. The workpiece forms the cathode and the tool, otherwise referred to as the electrode, forms the anode. The particles are washed away by the continuously flushing dielectric fluid.
The electrode for an electroerosion machine is generally manufactured from conductive materials such as graphite, brass, or copper. As noted above, a flow of dielectric fluid, such as a hydrocarbon oil, is pumped into the gap between the electrode and the workpiece to allow a path for the electrical discharge and to flush away debris from the arcing. A pulsating DC power supply is connected to supply the energy that provides the arcing between the electrode and the workpiece. The discharges travel through and ionize the dielectric fluid and sparks occur where the surfaces of the electrode and the workpiece are closest. The region in which the spark occurs is heated to such high temperatures that a small speck of the work surface is melted and removed from the workpiece, and is subsequently swept away by the flow of the dielectric fluid. This part of the workpiece is now below the average level of the workpiece surface so the next highest areas of the workpiece are removed next. These discharges occur hundreds or thousands of times per second so that gradually all of the area on the workpiece that is in communication with the electrode is eroded.
For the reasons mentioned above, electroerosion is useful in machining components for use in aeronautical and space applications. For example, electroerosion is used to machine cooling holes in super alloy components of gas turbine airfoils in circumstances where accessibility or hole shape complexity precludes the use of laser drilling, with such holes being formed via trepanning or drilling methods, Cooling holes are formed in the airfoil wall sections of nozzle guide vanes to enable cooling air fed, for example, from the engine compressor to pass from the hollow core of the nozzle guide vanes to form a thin film of cooling air over the airfoil surface, thereby protecting the airfoil from the effects of high temperature combustion gases.
However, one drawback to electromachining processes is that material recycling of the workpiece is difficult and expensive. That is, it is recognized that material recycling for expensive workpiece materials (e.g., titanium) is highly desirable; however, existing electroerosion techniques make recycling of the workpiece difficult as chips and shavings generated by electroerosion machining are difficult and expensive to recycle due to their small size and also due to oxidation thereof. Especially for electoerosion machining techniques utilized to provide a rough machining method that aggressively removes a large amount of material, material recycling is highly desirable based on the amount of material being machined.
Therefore, it is desirable to provide a means for recycling workpiece chips and shavings in electroerosion rough machining processes.